Good Day Sunshine: Vitamin D In Smart Doses Helps Avert Many Problems

titoOnz / Getty Images/iStockphoto

titoOnz / Getty Images/iStockphoto

JOSEPH A. O'BRIEN JR.

The sun's out, so go out and play.

If you're like me, you probably heard this admonishment more than once from your mother or a friend's mom while growing up. Yet despite how annoying the advice may have seemed when a favorite television show felt like a better option, health experts are moving ever closer to agreement that it's among the best pieces of advice any of us will get.

The benefits of exercise and fresh air aside, what we often fail to appreciate while outdoors is simply the sunlight — that life-sustaining energy that bestows a myriad of biochemical perks on us and the absence of which is extraordinarily bad for our health.

For reasons best understood by the biochemists and endocrinologists, the ultraviolet energy in sunlight converts a cholesterol-related compound found in the skin to vitamin D. A little more jiggering by native enzymes and some magic performed in the liver and kidneys and you get a bioactive hormone that regulates an array of biological functions ranging from bone formation to cell communication throughout the body.

Now, after years of telling us that too much sunlight is the enemy that leads to wrinkles and skin cancer, many scientists are adopting a more balanced position on sunlight. Evidence is growing that the right amount of vitamin D, derived from sunlight and diet, may play a role in preventing many ailments — including childhood asthma, some cancers, diabetes, autism and autoimmune disorders such as multiple sclerosis (MS) — or in reducing their severity. It also protects against acute respiratory tract infections that can trigger asthma attacks, particularly in children.

kieferpix / Getty Images/iStockphoto

kieferpix / Getty Images/iStockphoto

A recent study published in The Journal of Allergy and Clinical Immunology found that giving pregnant women supplements containing vitamin D3 boosted the immune system of newborns, protecting them from infections that could trigger asthma-related breathing problems.

The National MS Society cites research that suggests reduced levels of vitamin D in the blood are "a risk factor'' for developing MS, a disease in which myelin, a fat-like insulation surrounding nerve fibers, is stripped away by the body's own immune system, disrupting the signaling abilities of nerve cells. Researchers in Boston and Denmark have found that low levels of vitamin D in the blood of newborns raise the risk that they will develop MS later in life.

The connection between low levels of vitamin D and human diseases was noticed in the first decades of the 20th century, as doctors pondered the cause of rickets, a softening of bones among children that led to skeletal deformities. Although the disease was rampant among children of industrial workers in Scotland in the 17th century and among children of immigrants in the United States in the 19th and early 20th centuries, the connection to sunlight and food rich in vitamin D didn't gel until 1918, when a researcher discovered that cod liver oil prevented rickets in puppies.

A short time later, cod liver oil, which is a good source of vitamin D, was given to children to treat and prevent the disease.

As studies showing an association between vitamin D and better health have reached the public, sales of vitamin D supplements have climbed. In a five-year study (2009-2014) of vitamin D levels among residents of greater Danbury led by Dr. Joseph Belsky, an endocrinologist at Danbury Hospital and clinical professor of medicine at Yale University School of Medicine, it was noted that spending on vitamin D supplements, which had reached $40 million in 2001, ballooned tenfold to $425 million in 2009. Spending on vitamin D supplements nationwide reached roughly $750 million by 2014.

There's been "kind of a vitamin D craze in the last decade," Belsky said.

He noted that the position of the National Institutes of Health and the Endocrine Society has been that no evidence shows that taking vitamin D is helpful. "At the same time there is article after article after article matching low vitamin D with cancer, multiple sclerosis, but falling short of saying [it's the] cause."

It seems that patients and doctors who are up on the most recent studies about the potential benefits of vitamin D are hedging their bets by having their blood levels checked and taking supplements if necessary.

Groups at risk of vitamin D deficiency include breast-fed infants, older adults, people with limited sun exposure, people with dark skin (the pigment melanin reduces the skin's ability to produce vitamin D from sunlight), people with inflammatory bowel disease, which blocks fat absorption; obesity, which traps the vitamin, and people who have had gastric bypass surgery. Use of sunscreen — the stuff that in another annoying moment our moms slathered on our skin to reduce the risk of sunburn after we had been sent outside to play — also is considered a culprit in the widespread vitamin D deficiency.

The National Academy of Medicine estimates that roughly 50 percent of the general population lives with vitamin D levels well below the level that the Endocrine Society considers sufficient to maintain health.

So as the sun slides lower in the sky as we approach the fall and winter seasons, remember the advice that even dermatologists endorse these days: Get out in the sun for 20 minutes a day without sunscreen. And if that's not possible, consider adding an extra bowl of fortified cereal or a vitamin D3 supplement (this is the one recommended by most experts) to your daily routine. Your body may thank you.